1. Field of the Invention
The present invention relates to a semiconductor manufacture apparatus having a chemical regenerating function to be used in a semiconductor manufacture process.
2. Description of the Related Art
In general, in a semiconductor manufacture plant, a large amount of chemicals, such as sulfuric acid, hydrogen peroxide solution and the like are used in a semiconductor manufacture processes, such as wafer cleaning process, photoresist stripping process and so forth. Therefore, a large amount of waste liquid, such as waste acid, waste alkali and the like is generated to cause disposal problems. In recent years, for some kinds of chemicals used in large amounts, attempts have been made for collecting, refining and re-using the chemicals in the manufacture process, and thus development of regeneration methods of various waste products has been progressed.
However, when a size of a chemicals bath is increased due to increasing wafer diameter, the amount of chemicals to be used is inherently increased to increase not only the cost of the chemicals but also liquid waste disposing cost and environmental load. In this connection, it has been demanded a new technology to reduce the liquid waste amount as much as possible.
In the conventional semiconductor manufacture apparatus, when moisture content is accumulated due to decomposition of components in the chemicals, the chemicals are replenished to maintain the chemical concentration constant. For instance, sulfuric acid-hydrogen peroxide solution mixture, moisture content is accumulated in the chemicals due to deposition of hydrogen peroxide solution by heating or so forth, or by other cause, to lower concentration of sulfuric acid.
When the concentration of sulfuric acid in the solution is low, conversion amount into oxidizing substance, such as peroxomonosulfuric acid becomes small despite of the fact that large amount of hydrogen peroxide solution is contained in the chemicals thereby making it impossible to achieve satisfactory cleaning effect.
For this reason, not only hydrogen peroxide solution, but also a given amount sulfuric acid is replenished regularly to eliminate lowering the sulfuric acid concentration. However, when the concentration of sulfuric acid is lowered below a critical amount it becomes difficult to maintain cleaning performance and/or stripping performance at a given level or higher even when sulfuric acid is regularly replenished, therefore exchanging of the chemicals is performed.
Used chemicals are collected as a waste liquid and can be re-used for an application which does not require significantly high purity. A sulfuric acid refining device may be installed in a semiconductor manufacture plant for re-using sulfuric in the semiconductor manufacture process. For example, sulfuric acid regeneration device W-SARP100N-SD available from K.K. Wakomu Seisakusho can be such a sulfuric acid refining device. Japanese Unexamined Patent Publication No. Heisei 3-147323 discloses a cleaning system utilizing such a sulfuric acid refining device.
In Japanese Unexamined Patent Publication No. Heisei 3-147323, as shown in FIG. 5, a cleaning liquid to be used in the semiconductor manufacture process is first collected in a collection tank 102 through a pipeline 108. Then, impurities or moisture are subsequently removed in the sulfuric acid refining device 103 for refining high purity sulfuric acid.
In the above-identified publication, there has been disclosed a method, in which sulfuric acid is fed to a chemicals supply device 104 incorporating a chemicals tank, and when a substrate cleaning device requires an additional supply of the chemicals, high purity chemicals are supplied from the supply device to a cleaning device 101.
However, since the foregoing sulfuric acid refining device performs refining of high purity sulfuric acid by distillation, oxidizing substances, such as hydrogen peroxide, peroxomonosulfuric acid and the like in the mixture are completely decomposed during distillation. Therefore, through the foregoing process, only sulfuric acid can be regenerated. Therefore, upon re-use, hydrogen peroxide has to be newly mixed to make it difficult to reduce the required amount of hydrogen peroxide.
In Japanese Unexamined Patent Publication No. Heisei 5-139707, as shown in FIG. 6, there has been disclosed a method, in which waste sulfuric acid is supplied to a cathode chamber 123 of a two chamber type refining electrolytic bath 121 by an anion exchange membrane 122, for electrolysis, and sulfuric acid obtained from anode chamber 124 of the two chamber type refining electrolytic bath 121 is electrolyzed in the anode chamber 128 of a two bath type condensing electrolytic bath 125 separated by a cation exchange membrane 126, to perform condensation of sulfuric acid and refining of an oxidizing substance, in order to avoid lowering performance of the oxidizing substance upon regeneration.
However, the cleaning system disclosed in Japanese Unexamined Patent Publication No. Heisei 3-147323 requires replenishing of chemicals in the method similar to the prior art when moisture content is accumulated in the chemicals and thus lowers cleaning performance. As with the system of FIG. 5, oxidizing substances, such as hydrogen peroxide and the like are completely removed. Therefore, the required amount of hydrogen peroxide cannot be reduced. Therefore, as a method for removing only moisture content from the chemicals, distillation method is not effective in view of energy required. Also, the disclosed method cannot reduce number of required chemical changes and thus do not aid in improving throughput over conventional methods.
On the other hand, the method disclosed in Japanese Unexamined Patent Publication No. Heisei 5-139707, a long period of 150 to 170 hours is required for refining and condensing the chemicals of 1000 ml as shown in the embodiment. Therefore, it is not possible to perform continuous process by actually installing in the manufacture device.